The present invention relates to novel compounds and more particularly to novel yellow pigments which are useful in the photoelectrophoretic imaging method.
Photoelectrophoretic imaging methods which are capable of producing monochromatic or polychromatic images are described and claimed in various U.S. Patents including, for example, U.S. Pat. Nos. 3,384,565; 3,384,566; and 3,385,488. In photoelectrophoretic imaging there is provided an imaging suspension which comprises imaging particles suspended in a carrier liquid. Typically, a layer of the imaging suspension is arranged between a pair of electrodes, subjected to an applied electrical field and exposed to an imagewise pattern of activating electromagnetic radiation. At the completion of these method steps, there are typically formed complementary images at the surfaces of the electrodes. An essential component of the photoelectrophoretic imaging system is the imaging particles which must be electrically photosensitive and which apparently undergo a net change in charge polarity upon exposure to activating electromagnetic radiation through interaction with one of the electrodes. The imaging particles used in this imaging system should have intense pure colors and be highly photosensitive.
The prior art teaches various types of pigments which are suitable for use in photoelectrophoretic imaging. Further, other prior art disclosures which are unrelated to photoelectrophoretic imaging teach compounds which may be found to be useful in this imaging system. For example, the preparation of 2-bromo-3,4-benzobrazanquinone is described in "Proceedings of the Indian Academy of Science", B. Suryanarayana and B. Tilak, page 81, 1953, and 2-chloro-3,4-benzobrazanquinone is described in German Pat. No. 461,650. These compounds are yellow pigments. Nevertheless, there continue to be discovered new pigments which may be used in the photoelectrophoretic imaging mode. The present invention relates to novel yellow pigments which may be used in such an imaging system.